docs: def lowshelf(self, gain=-20.0, frequency=100, slope=0.5):
          """lowshelf takes 3 parameters: a signed number for gain or attenuation
          in dB, filter frequency in Hz and slope (default=0.5, maximum=1.0).
  
          Beware of Clipping when using positive gain.
          """
          self.command.append('bass')
          self.command.append(gain)
          self.command.append(frequency)
          self.command.append(slope)
          return self